This invention relates to a method for electrical bonding of LLCCC-components on printed circuit boards.
The use of LLCCC (Leadless Ceramic Chip Carrier) components in space technology has so far been possible only on ceramic substrates or special substrates with adapted coefficients of expansion, due to the very different physical characteristics of the component and the printed circuit board. These surface-mountable integrated circuits are situated in a hermetically sealed ceramic housing, and no longer have any flexible connections; thus, the multiple bonding--up to 68 connections--to the ceramic substrate must be established by way of soldering surfaces. FIG. 1 of the drawing illustrates a standard bonding for LLCCC-components according to the state of the art. This bonding technique, however is not sufficiently reliable for the use of such components on printed circuit boards in space technology because the stress resulting from temperature changes encountered in such applications causes excessive expansion problems.
It is an object of the invention to provide a bonding method which permits the use of LLCCC-components in electronic systems for space applications, and which reliably accommodates the high temperature stress which occurs on these components in a space environment.
This object is achieved by the use of specially shaped flexible bonding elements to secure the LLCCC component to the printed circuit board. In a preferred embodiment, the bonding elements are bent to a semicircular curvature which provides the flexibility necessary to .absorb stresses due to differing coefficients of thermal expansion among the various components.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.